The Adult AIDS Clinical Trials Group (ACTG) is a multicenter, multidisciplinary investigative group dedicated to the study of HIV-1 pathogenesis and therapy. Operating since 1987 under a collection of grants and contracts sponsored by the National Institute of Allergy and Infectious Diseases, the ACTG formerly addressed both adult and pediatric manifestations of HIV disease. Following a reorganization, there are now separate structures for an Adult ACTG and a Pediatric ACTG. This cooperative agreement concerns the Adult ACTG Central Group, which includes support for the Group Leader, the Executive Committee, other standing committees, a Community Constituency Group, the Operations Office, and the Advanced Technology Laboratories. Associated with the Central Group, under separate applications, are 22-29 AIDS Clinical Trial Units and a Statistical and Data Management Center. The Central Group will initiate 24-30 clinical trials per year that will enroll 2,500 to 3,500 study participants. The Group will be managed by an Executive Committee that will oversee an integrated research agenda developed by three Research Advisory Committees (HIV Disease, Complications of HIV Disease, and Immunology/Immune-Based Therapy). The structure of the Adult ACTG has been designed to provide a mechanism for a coordinated response to rapidly changing investigative opportunities. Clinical trials will be designed to delineate therapeutic approaches that both improve the survival and quality of life for persons with HIV-1 infection and make use of therapeutic interventions to further define the pathogenesis of HIV-1 infection. The increased emphasis on the investigation of HIV-1 pathogenesis is reflected by a major increase in the resources devoted to laboratory investigation. The ACTG will devote considerable effort and resources to the recruitment and retention of individuals that reflect the changing demographics of the AIDS epidemic. This effort is reflected in recruitment plans of individual units, and by the inclusion of four clinical trials units based at traditionally minority institutions.